Electrode Interface System

ABSTRACT

An electrode interface system for providing a connection between at least one electrode and a maternal-fetal monitor, wherein the interface system converts electrical muscle activity captured by the electrode(s) into uterine activity data signals for use by the maternal-fetal monitor. The electrode interface system of the invention preferably includes a conversion means for converting the signals from the electrode(s) into signals similar to those produced by a tocodynometer.

CROSS-REFERENCE TO A RELATED APPLICATION

This application is a continuation application of U.S. Ser. No.11/582,714, filed Oct. 18, 2006, which is incorporated herein byreference in its entirety.

BACKGROUND OF INVENTION

Assessment of the fetus during pregnancy, and particularly during laborand delivery, is an essential yet elusive goal. While most patients willdeliver a healthy child with or without monitoring, more than 5 out ofevery 1,000 deliveries of a viable fetus near term are stillborn, withhalf having an undetermined cause of death. (National Vital StatisticsSystem (NVSS), CDC, NCHS as published in “Healthy People 2010,Understanding and Improving Health: Chapter 16,” co-authored by theCenters for Disease Control and Prevention and Health Resources andServices Administration, 2^(nd) Edition, U.S. Government PrintingOffice, November 2000). The risk of this unfortunate consequence isincreased in a subgroup of “high risk” patients (e.g., diabetics). Inaddition to regular obstetric observation, after 23 weeks gestationantepartum (“in utero”) fetal monitoring consists of the following (inorder of complexity):

-   -   1. maternal report of fetal movement;    -   2. non-stress test (NST)—monitor fetal heart rate (FHR) by        ultrasound, looking for baseline rate, variability and presence        of accelerations above the baseline;    -   3. contraction stress test (CST)—response of the FHR to uterine        contractions, either natural or induced; and    -   4. biophysical profile (BPP)—NST plus ultrasonographic        evaluation of fetal movements and amniotic fluid volume.

Despite their wide acceptance, these tests offer limited predictivevalue, and give only a glimpse of the fetus at the time of testing. Forhigh risk patients, once or twice weekly surveillance is oftenindicated, entailing both expense and inconvenience for the patient.

Intrapartum fetal surveillance is accomplished routinely withintermittent auscultation or continuous Doppler monitoring of the FHR,together with palpation or tocodynamometry (strain gauge) monitoring ofcontractions. When indicated, more invasive monitors are available, butrequire ruptured membranes/adequate cervical dilation, and entail somerisk, primarily infectious. These monitors include, without limitation:

-   -   1. fetal scalp electrode—a wire electrode inserted into the        fetal scalp;    -   2. intra-uterine pressure catheter (IUPC)—enables quantitative        measurement of contractions; and    -   3. fetal scalp sampling—a blood sample drawn for pH analysis.

Contraction detection allows monitoring of the progress of labor. Adevice commonly used in monitoring contractions is the tocodynamometer.The tocodynamometer detects physical changes in the curvature of themother's abdomen (usually with a strap or belt that is placed about theabdomen) during a contraction and translates these changes into aprinted curve. The tocodynamometer detects only the presence or absenceof tension on the abdomen (whether from uterine contraction or maternalmovement), and often fails in the presence of obesity. Unfortunately,patients are recommended to remain in a supine position when using atocodynamometer to monitor labor, which has been found to be the leasteffective physiological position for encouraging fetal internal rotationand often causes maternal hypotension and discomfort.

When cervical dilation lags behind the anticipated labor curve, oxytocinis often indicated to induce a more effective contraction pattern. Safetitration of the oxytocin may require accurate determination of“montevideo units” which measure the strength of uterine contractionsover 10 minutes. This requires the more invasive IUPC, a catheter placedinto the uterus, alongside the fetus, to measure the pressure generatedby uterine contractions.

The rationale for use of intrapartum electronic fetal monitoring (EFM)assumes that FHR abnormalities accurately reflect hypoxia (inadequateoxygen to the fetus), and that early recognition of this could induceintervention to improve outcome for both mother and fetus.Unfortunately, numerous studies have failed to identify this improvedoutcome with the use of EFM in low-risk deliveries. In fact some studieshave actually shown an increase in morbidity from a higher operativedelivery rate. Perhaps this should not be surprising in light of thevariability in interpretation of FHR tracings and their lack ofspecificity for hypoxia. Yet, continuous EFM remains the standard ofcare in US hospitals, in large part due to medical and legal concerns.

Uterine contractions are the result of the coordinated actions ofindividual myometrial cells. At the cellular level, the contractions aretriggered by a voltage signal called an action potential. Duringpregnancy, cellular electrical connectivity increases such that theaction potential propagates to produce a coordinated contractioninvolving the entire uterus. The action potential during a uterinecontraction can be measured with electrodes placed on the maternalabdomen resulting in a uterine EMG signal (hereinafter referred to as“EHG”: electrohysterogram). Specifically, the EHG signal can beprocessed to produce a signal that is similar to the standard uterineactivity signal from the tocodynamometer or IUPC. The EHG providescontraction frequency and duration information. To date, EHG signalshave not been used in assessing the intra-uterine pressure or predictingmontevideo units.

Postpartum, continuous uterine contraction is required to minimizeuterine bleeding from the placental detachment site. Hemorrhage is theleading cause of peripartum maternal death, and most of these arepostpartum hemorrhage due to this “uterine atony.” Current monitoringconsists of serial uterine palpation at intervals of several hours.Diagnosis is usually made by patient complaint of severe bleeding, orhypovolemic shock (from hemorrhage). Neither IUPC nor tocodynamometermonitoring is available at this time. The EHG would provide a uniquemeans for monitoring the uterine tone, providing an early warning ofatony and potential hemorrhage.

Devices that utilize invasive techniques for monitoring fetal healthinclude those disclosed in U.S. Pat. Nos. 6,594,515; 6,115,624;6,058,321; 5,746,212; 5,184,619; 4,951,680; and 4,437,467.

Accordingly, a cost-effective, more reliable system and method fornon-invasively measuring uterine activity, in particular contractionsduring labor, without the need for expensive equipment replacement wouldbe beneficial.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a unique interface system that convertselectrical muscle activity captured by common electrodes (such as forECG/EMG) into signals that provide uterine activity data to amaternal-fetal monitor without the use of a tocodynamometer. Preferably,the interface system comprises a cable that converts output fromelectrodes to an output comparable to those provided by atocodynamometer for connection to a maternal-fetal monitor configuredfor a uterine activity sensor (such as a tocodynamometer, anintrauterine pressure catheter, a fetal scalp electrode, and the like).

In one embodiment, the interface system of the invention comprises aninterface (also referred to herein as a connector) for at least oneelectrode, an interface for a compatible port in a maternal-fetalmonitor, and a signal converter for converting electrode output providedthrough the electrode interface to output comparable to those providedby a tocodynamometer.

In one embodiment, the interface system comprises a cable portion formedintegrally with an electrode interface, a maternal-fetal monitor portinterface, and a signal converter to provide a unitary cable structure.In another embodiment, the interface system comprises an electrodeinterface that includes a wireless signal transmitter, a maternal-fetalmonitor port interface, and a signal converter that includes a wirelesssignal receiver, wherein all of these components are physicallyindependent from each other.

In a preferred embodiment, the interface system comprises an electrodeinterface for multiple electrodes, more preferably between 2 and 6electrodes. Preferably, the maternal-fetal monitor port interface isoperably connectable with a uterine activity port or a tocodynamometerport available on the maternal-fetal monitor.

The present invention provides a new and improved interface system thathas the ability to provide accurate contraction data by convertingelectrode signals into tocodynamometer-comparable data that can beprocessed using commercially available maternal-fetal monitors. Thepresent invention is particularly advantageous because of low costs ofmanufacture with regard to both materials and labor, which accordinglyinduces low prices of sales to the consuming public.

Other features and advantages of the invention will be apparent from thefollowing description and accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates one embodiment of the invention wherein an interfacecable of the invention is operatively connected to a strip of electrodesand a maternal-fetal monitor.

FIG. 2 illustrates a power adapter that can be used in combination withthe interface cable of the invention.

FIG. 3 illustrates a strip of electrodes that can be used in combinationwith the interface cable of the invention.

FIG. 4 is a flow diagram illustrating the process for convertingelectrode input to tocodynamometer-like data within the interface cable.

FIG. 5 illustrates another embodiment of the invention comprising awireless interface connection between an electrode strip andmaternal-fetal monitor.

FIG. 6 illustrates one process for producing an electrical analogequivalent to a tocodynamometer signal from electrode signals.

FIG. 7 illustrates a uterine activity connector pinout in amaternal-fetal monitor.

FIGS. 8A-8C illustrate a square-type cable for interfacing a fetal scalpelectrode with a maternal-fetal monitor, including the cable pinoutdiagram and a “square-type” connector pinout for the fetal scalpelectrode cable in a maternal-fetal monitor.

FIGS. 9A-9C illustrate another cable for interfacing a fetal scalpelectrode with a maternal-fetal monitor, including the cable pinoutdiagram and a “circular-type” connector pinout for the fetal scalpelectrode cable in a maternal-fetal monitor.

FIGS. 10A-10C illustrate a cable for interfacing an intra-uterinepressure catheter (IUPC) with a maternal-fetal monitor, including thecable pinout diagram and a “circular-type” connector pinout for the IUPCcable in a maternal-fetal monitor.

FIGS. 11A-11C illustrate yet another cable for interfacing a fetal scalpelectrode with a maternal-fetal monitor, including the cable pinoutdiagram and the corresponding connector pinout for the fetal scalpelectrode cable in a maternal-fetal monitor.

FIGS. 12A-12D illustrate another cable for interfacing an intra-uterinepressure catheter (IUPC) with a maternal-fetal monitor, including thecable pinout diagram and the corresponding connector pinout for the IUPCcable in a maternal-fetal monitor.

FIG. 13 illustrates a tocodynamometer connector pinout in amaternal-fetal monitor.

FIG. 14 illustrates the differences in accuracy for contraction patternsmonitored in obese women with a tocodynamometer versus EHG-derivedcontraction patterns.

FIG. 15 illustrates a maternal-fetal monitor including a connectorpinout suitable for use with the interface cable of the invention.

DETAILED DISCLOSURE

The present invention provides a unique interface system that convertselectrical muscle activity signals captured by at least one electrodeinto signals that provide uterine activity data to a conventionalmaternal-fetal monitor without the use of a tocodynamometer or invasivematernal-fetal monitoring device (such as an intra-uterine pressurecatheter (IUPC) or fetal scalp electrode). The information provided bythe interface system can then be processed by the maternal-fetal monitorto generate information regarding EHG signals, uterine contractionduring and after labor, uterine atony, intrauterine pressure, Montevideounits, and the like.

In one embodiment, as illustrated in FIG. 1, the interface systemcomprises a cable integrally formed with an electrode interface 10 (oralso referred to herein as a connector), a maternal-fetal monitor portinterface 20, and a signal converter 15 that converts output signalsfrom electrodes to an output signal comparable to those provided by atocodynamometer or IUPC. The interface system is preferably in the formof a unitary cable structure. The electrode interface 10 can beconnected to any conventional electrode or set of electrodes 5.

The cable can transmit analog, digital, or a combination of analog anddigital signals. In certain embodiments, the cable is specificallydesigned for communication/connection with a conventional maternal-fetalmonitor 25. For example, a cable can be preprogrammed with the expectedvoltage range for the monitor.

In a related embodiment, the cable uses the same power as that suppliedby the maternal-fetal monitor, and thus will not require a separatepower supply. In certain embodiments, as illustrated in FIG. 2, anadditional power connector is included in the system that allows forpermanent power connectivity. The power connector can be designed as asemi-permanent adapter 30 connected to the maternal-fetal monitor thatallows both standard tocodynamometer (or IUPC) cables 35 and an EHGcable 40 to be plugged into it without removing the adapter from themonitor 25. In this way, the power system can be attached to the monitoronce and not removed, allowing repeated swapping of the tocodynamometer(or IUPC) cable and the interface system of the present inventionwithout undue hassle.

The electrode interface can be connected to any conventional electrodeor set of electrodes including, but not limited to, disposableelectrodes (including electrodes that are without gel and pregelled),reusable disc electrodes (including gold, silver, stainless steel, ortin electrodes), headbands, and saline-based electrodes. Contemplatedelectrodes include those used for monitoring electrocardiography(ECG/EKG); electroencephalography (EEG); electromyography (EMG);electonystagmography (ENG); electro-oculography (EOG), printed circuitelectrodes, and electroretinography (ERG).

In a preferred embodiment, as illustrated in FIG. 3, the interfacesystem comprises an electrode interface for a plurality of electrodes,more preferably between 2 and 6 electrodes. Preferably, the electrodesare provided on a strip or mesh 5, including a single connector 10 forthe electrode interface of the invention. The electrodes can be bipoloror monopolar in nature. The electrodes are preferably AgAgCl sensorswith a surface area of 27 mm² wet gel. In certain related embodiments,there is an adhesive area surrounding the sensor area. The electrodescan be placed in a wide variety of locations on the patient, includingover the uterus.

In the preferred embodiment, the signal converter of the inventionincludes a microprocessor, digital signal processor, or otherprogrammable device that converts electrode signal data into anelectrical analog of a Wheatstone bridge configuration that is normallyused in a tocodynamometer. An illustration of a Wheatstone bridgeconfiguration used in a conventional tocodynamometer is illustrated inFIG. 6. A tocodynamometer generally transforms strain to the straingauge/sensor into a proportional change of resistance. Given the linearWheatstone bridge configuration, differential output voltages areproduced that are linearly related to the strain applied to thegauge/sensor. These differential output voltages are produced at the (+)and (−) pressure ports at mV amplitude levels. In certain instances,these small differential output voltages are subsequently amplified inthe fetal/maternal monitor using a differential-input instrumentationamplifier configuration.

According to one embodiment of the subject invention, as illustrated inFIG. 4, the signal converter 15 includes a programmable device 55 and ananalog to digital converter 50 that converts EHG signals derived fromthe electrode interface from analog signals to a digital output, wherethe digital output is then processed by the programmable device. Theprogrammable device determines the appropriate voltage level required tomimic the output of the tocodynamometer or IUPC based upon the EHGdigital output signals received. This voltage level can then beconverted back to an analog signal using a digital to analog converter60, pulse width modulation circuit, or other method.

In another embodiment, the signal converter includes a microprocessor 55that calculates the desired uterine activity from the EHG signals. Themicroprocessor interfaces to the monitor via a microprocessor-controlleddigital potentiometer, where the potentiometer simulates the straingauge resistances seen at the legs of the Wheatstone bridge. Thissolution would mimic the tocodynamometer itself, instead of just thevoltages output from the tocodynamometer. The desired signal would bedriven on the Weatstone bridge in a matter similar to thetocodynamometer itself, thus creating an EHG emulation of atocodynamometer that is more compatible with different types of fetalmonitors.

In certain embodiments, the microprocessor includes a means forfiltering 45 of the signals generated from the electrodes. In oneembodiment, the microprocessor includes: (1) a high pass filter at verylow frequency (0.005 Hz) to remove the DC offset and noise, and (2) alow pass filtered with another low frequency filter (0.025 Hz). In arelated embodiment, the microprocessor includes a high pass filter at avery low frequency and a standard power estimation method such as RMS orother squaring methods. More complex signal processing methods such aswavelets, blind source separation, nonlinear filtering, and frequencyanalysis can also be utilized.

Multiple signal channels can be included at the electrode interface toreduce noise characteristics. The multiple channels can be processed bythe signal converter in many ways. For example, the signals can simplybe added to each other or subtracted from each other for more robustnessto noise. Additionally, attributes can be calculated on each signal andthose signals with the best characteristics (e.g. signal to noise ratio)can be used to create the uterine activity signal.

In an alternative embodiment, the microprocessor and digital portion ofthe system would be replaced with a completely analog system. Analogfilters can be created with resistors, capacitors, and amplifiers can beembedded into the signal converter to convert the DIG signals totocodynamometer-like signals. Analog circuitry can be designed usingdiscrete components or integrated components such as ASICs (applicationspecific integrated circuits). Since the conversion from EHG electricalinterface to tocodynamometer or IUPC electrical interface is externally,simply a voltage conversion, analog filtering can be created to modifythe EHG signals and create signals that mimic those expected by thefetal monitor.

In yet another embodiment, the signal converter includes both analog anddigital processing. The analog processing would typically include pre-or post-processing of the signals. For example anti-aliasing filters orother filtering techniques can be implemented by the signal converter.Similarly, the signal converter could apply signal conditioning to theoutput signal to appropriately mimic the signal output from atocodynamometer or IUPC.

A wireless embodiment is contemplated herein, see FIG. 5. The interfacesystem comprises an electrode interface 10, a wireless signaltransmitter 65, a wireless signal receiver 70, a signal converter 15,and a maternal-fetal monitor port interface 20. According to the subjectinvention, these components can be physically independent from eachother or presented in various combinations to form a single component.For example, the electrode interface and wireless signal transmitter canbe presented together as a single component; the wireless signalreceiver and signal converter can be presented together as a singlecomponent; the signal converter and wireless signal transmitter can bepresented together as a single component; the maternal-fetal portinterface, the signal converter, and the wireless signal receiver can bepresented together as a single component.

According to one embodiment, a wireless signal transmitter is operablyconnected to an electrode interface, which is connected to theelectrode(s). The wireless signal transmitter can include a data storagedevice (such as a magnetic hard drive, flash memory card, and the like).Preferably, the wireless signal transmitter includes communicationsprotocols for data representation, signaling, authentication, and errordetection that is required to send information over a wirelesscommunications channel (i.e., a specific radio frequency or band offrequencies such as Wi-Fi, which consists of unlicensed channels 1-13from 2412 MHz to 2484 MHz in 5 MHz steps). The wireless signaltransmitter is preferably located in close proximity to the patient oron the patient's body. For example, the wireless signal transmitter canbe attached to the side of the bed or the patient's arm. In certainembodiments, the signal converter is operably connected to the wirelesssignal transmitter or presented together with the wireless signaltransmitter as a single component.

A wireless signal receiver is also included in the wireless embodiment.The wireless signal receiver is operably connected to a signal converterand/or maternal-fetal monitor port interface. The wireless signalreceiver is preferably configured with communications protocols toreceive information over a wireless communications channel.

Many wireless transmission communications protocols exist and areapplicable to the wireless signal transmitter/receiver of thisinvention, including Bluetooth, Wi-Fi, Zigbie, wireless USB, etc. Thewireless transmission of information from the wireless signaltransmitter to the wireless signal receiver could be in digital formator in analog format.

In certain embodiments, the wireless signal transmitter (and/or wirelesssignal receiver) includes an internal power source (i.e., batteries, andthe like). Alternatively, the wireless signal transmitter (and/orwireless signal receiver) does not require an internal power source.This is accomplished by using an antenna to convert radiated or inductedpower into usable energy for the transmission of the desired signals.For example, the wireless signal transmitter can be an antenna that iscommonly used in radio frequency identification tags (or RFID tags),where minute electrical current induced in the antenna by an incomingradio frequency signal provides just enough power for an integratedcircuit (IC) in the RFID tag to power up and transmit a response (forexample, to a wireless signal receiver of the invention).

In another embodiment, the EHG signal is digitized and stored in memoryeither in the electrode interface, the signal converter, or thematernal-fetal monitor port interface. The stored data can betransmitted periodically or at a later time. This delayed transmissionmay, without restriction, be utilized to improve battery life bytransmitting data transiently, instead of continuously; or to allow forpatient monitoring during disconnection from the monitor.

In operation, the electrode interface accepts DIG signals from theelectrode(s) and transmits the signals to the maternal-fetal portinterface via the wireless signal transmitter and wireless signalreceiver. The signal converter can be operably connected to either thewireless signal transmitter or the wireless signal receiver, where thesignal converter processes the electrode signals and/or performsdigital/analog signal conversions.

In one embodiment, the electrode interface attached to the electrodescontains a signal converter that can perform analog to digitalconversion and process MO signals into an equivalent tocodynamometer orIUPC voltage. The wireless signal transmitter would then digitallytransmit this data to the wireless signal receiver, which wouldcommunicate the data through the maternal-fetal port interface to thematernal-fetal monitor. Preferably, the data provided to thematernal-fetal monitor mimics data format normally provided by atocodynamometer or IUPC.

In another embodiment, the electrode interface includes a means forconverting analog signals to digital signals, and the resultant digitalsignals are transmitted via the wireless signal transmitter to thewireless signal receiver. The wireless signal receiver is operablyconnected to a signal converter that processes the digital signals intoa format equivalent to tocodynamometer or IUPC data, which issubsequently communicated to the maternal-fetal monitor via thematernal-fetal monitor port interface.

In yet another embodiment, the raw analog signals generated by theelectrodes are communicated via the electrode interface and wirelesssignal transmitter to a wireless signal receiver. The wireless signalreceiver is operably connected to a signal converter that converts theraw analog signals to digital signals, which are subsequently processedby the signal converter into a format equivalent to tocodynamometer orIUPC data. The tocodynamometer or IUPC data is subsequently communicatedto the maternal-fetal monitor via the maternal-fetal monitor portinterface.

According to the present invention, the electrode interface can also beoperably connected to a fetal heart rate sensor (such as an ultrasoundor fetal scalp electrode). Data collected from the fetal heart ratesensor can be communicated to a maternal-fetal monitor via the cableembodiment or the wireless embodiment described above.

As illustrated in FIG. 15, the maternal-fetal monitor port interface ofthe invention can be operatively connected to a maternal-fetal monitorport 80 (also referred to herein as a pinout) configured for aconventional uterine activity sensor (such as a tocodynamometer, anintrauterine pressure catheter, a fetal scalp electrode, and the like).Preferably, the maternal-fetal monitor port interface is operablyconnectable with a uterine activity port or a tocodynamometer portavailable on a conventional maternal-fetal monitor 85.

Maternal-fetal monitor port interface preferably consists of appropriateconnectors to maternal-fetal monitors from different manufacturershaving different pinout/port configurations (see FIGS. 7-13). One suchexample of interfacing to both COROMETRICS® and AGILENT® is provided bythe METRON® PS-320 patient simulator. This simulator uses a number ofcustom cables for interface to these monitors. Pinout/port informationfor commonly available maternal-fetal monitors are provided in Table 1:

TABLE 1 Uterine Activity Connector Pinout for Corometrics 116 MonitorPin # Signal Name Signal Description 1 (+) Pressure Positive Input toPressure Amp 2 (−) Pressure Negative Input to Pressure Amp 3 NC NoConnection 4 +4 Volt Excitation +4 Volt Reference to Bridge 5 NC NoConnection 6 GND (Excitation Ref) +4 Volt Reference Ground 7 UA ShieldShield 8 NC No Connection 9 NC No Connection 10 NC No Connection 11 IUPEnable IUP ENABLE (ACTIVE LOW) 12 TOCO Enable TOCO ENABLE (ACTIVE LOW)

Example 1

As noted above, labor contractions are typically monitored with a straingauge (such as a tocodynamometer), which provides frequency andapproximate duration of labor contractions. Unfortunately, in obesepatients, the distance from the skin to the uterus may be such that thetocodynamometer does not detect contractions reliably. In this setting,or when quantitative measurement of intrauterine pressure (IUP) isdeemed necessary, an invasive IUP catheter (IUP) is commonly required.The electrical activity of the uterus, or electrohysterogram (EHG) asmonitored using electrodes, has long been recognized as linked tomechanical activity. This Example provides a study that compared theaccuracy of EHG-derived contractions with those provided by atocodynamometer and IUP monitoring in clinically severely obese laboringwomen.

Participants

This Example evaluated data from 14 laboring subjects with body massindex (BMI)≧34 who had an IUPC placed during EHG monitoring. 30 minutesegments were selected before and after placement.

Methods

An array of eight 3-cm²Ag/AgCl₂ electrodes was placed over maternalabdomen and signals amplified with high gain, low noise amplifiers. Allsignals were measured with respect to a reference electrode, with drivenright leg circuitry to reduce common mode noise. The amplifier 3 dBbandwidth was 0.1 Hz to 100 Hz, with a 60 Hz notch. The contractionlocation was derived by down-sampling the signal at 20 Hz. Contractionswere rejected if duration was less than 30 seconds or greater than 120seconds, with an amplitude less than 30% of the median of the last 10contractions (a minimum amplitude of 5 units was also applied for eachtocodynamometer/IUPC). The contraction correlation index (CCI)⁽¹⁾=#consistent contractions/½(# tocodynamometer/IUPC−derived contractions+#ENG-derived contractions) was evaluated. In addition, the frequency ofunreliable uterine activity monitoring, using IUP as the standard forcomparison, was also evaluated.

Results

Of the 14 patients (BMI 45.1±7.9), 6 underwent amniotomy at the time ofIUPC placement. During the first half of the study, the tocodynamometeridentified 155 contractions while the EHG identified 195 contractions.After placement of the IUP, the IUP identified 192 contractions, versus185 EHG-derived contractions. The CCI between EHG and thetocodynamometer was 0.79±0.29 and the CCI was 0.92±12 between EHG andIUP (p=0.07, ns). These results demonstrate that the tocodynamometer maybe unreliable in clinically severely obese patients. As illustrated inFIG. 14, the EHG-derived contraction pattern in the obese women in thisstudy correlated better with IUP than the tocodynamometer, exceeding 90%correlation in 13/14 patients versus 10/14 for the tocodynamometer.

All patents, patent applications, provisional applications, andpublications referred to or cited herein are incorporated by referencein their entirety, including all figures and tables, to the extent theyare not inconsistent with the explicit teachings of this specification.

It should be understood that the examples and embodiments describedherein are for illustrative purposes only and that various modificationsor changes in light thereof will be suggested to persons skilled in theart and are to be included within the spirit and purview of thisapplication.

1. An interface system for interfacing multiple types of sensors to beinterfaced to a maternal-fetal monitor that is not part of the interfacesystem, wherein the interface system comprises: a signal converter forprocessing at least one signal into output data that mimics electricaloutput from a tocodynamometer or intra-uterine pressure catheter; and amaternal-fetal monitor port interface for operably and physicallyconnecting to the maternal-fetal monitor; wherein the signal converterand the maternal-fetal monitor port interface are integrated into acable-less, unitary adapter or connector.
 2. An interface systemcomprising: a wireless signal receiver for receiving at least onewireless signal from at least one sensor; a signal converter connectedto the wireless signal receiver, wherein the signal converter processesthe at least one signal into output data that mimics electrical outputfrom a tocodynamometer or intra-uterine pressure catheter; and amaternal-fetal monitor port interface for operably and physicallyconnecting to a maternal-fetal monitor; wherein the wireless signalreceiver, the signal converter, and the maternal-fetal monitor portinterface are integrated to form a unitary structure.
 3. The interfacesystem according to claim 2, wherein the at least one sensor is not atocodynamometer or intra-uterine pressure catheter sensor.
 4. Theinterface system according to claim 2, wherein the interface system isan interface cable.
 5. The interface system according to claim 2,wherein the interface system is a unitary adaptor or connector such thatthe wireless signal receiver, the signal converter, and thematernal-fetal monitor port interface are all contained in the unitaryadaptor or connector.
 6. An interface system comprising: a sensorinterface for operably connecting to at least one electrode andreceiving at least one electrode signal from the at least one electrode;a signal converter connected to the sensor interface, wherein the signalconverter processes the at least one signal into output data that mimicselectrical output from a tocodynamometer or intra-uterine pressurecatheter; and a wireless signal transmitter for wirelessly transmittingthe output data to a maternal-fetal monitor; wherein the sensorinterface, the signal converter, and the wireless signal transmitter areintegrated to form a unitary structure.
 7. The interface systemaccording to claim 6, wherein the interface system is an interfacecable.
 8. The interface system according to claim 6, wherein theinterface system is a unitary adaptor or connector such that the sensorinterface, the signal converter, and the wireless signal transmitter areall contained in the unitary adaptor or connector.
 9. An interfacesystem comprising an electrode interface, a maternal-fetal monitor portinterface, and a signal converter, wherein the signal converterprocesses two or more signals from at least one electrode operablyconnected to the electrode interface and combines the two or moresignals into a single stream of output data that is comparable totocodynamometer or intra-uterine pressure catheter output.
 10. Theinterface system according to claim 9, wherein the interface system isan interface cable.
 11. The interface system according to claim 9,wherein the signal converter combines the two or more signals based onaveraging the two or more signals.
 12. The interface system according toclaim 9, wherein the signal converter combines the two or more signalsbased on selecting best features of each of the two or more signals. 13.The interface system according to claim 9, wherein the signal convertercombines the two or more signals based on a weighted average of the twoor more signals, wherein the weighted average is based on signalcharacteristics.
 14. An interface system comprising an electrodeinterface, a maternal-fetal monitor port interface, and a signalconverter, wherein the signal converter processes at least one signalfrom at least one electrode operably connected to the electrodeinterface and converts the electrode signal(s) into output datacomparable to tocodynamometer or intra-uterine pressure catheter output;wherein the interface system is designed to connect to differentmaternal-fetal-monitors without modification.
 15. The interface systemaccording to claim 14, wherein the interface system further comprises acable portion, wherein the cable portion is formed integrally with theelectrode interface, the maternal-fetal monitor port interface, and thesignal converter to provide a unitary cable structure.